A team of cold-case investigators claim they’ve decoded a 1972 message by D.B. Cooper — and that it contains a confession from Vietnam veteran Robert Rackstraw, long suspected of being the infamous skyjacker.

The letter was addressed to “The Portland Oregonian Newspaper.”

Months earlier, a man identified as the fictitious Cooper had hijacked a Seattle-bound flight and later parachuted out of a plane with $200,000, never to be heard from again.

“This letter is too (sic) let you know I am not dead but really alive and just back from the Bahamas, so your silly troopers up there can stop looking for me. That is just how dumb this government is. I like your articles about me but you can stop them now. D.B. Cooper is not real,” it reads.

“I want out of the system and saw a way through good ole Unk,” he writes. “Now it is Uncle’s turn to weep and pay one of it’s own some cash for a change. (And please tell the lackey cops D.B. Cooper is not my real name).”

“No one even knew about this letter,” Colbert told the Daily News. “When I got it, I noticed it was typed just like (a different Cooper letter), so I called a code breaker and showed it to him. He said, ‘Tom, you’re not going to believe it, but his confession is in here,'” Colbert said.

Rick Sherwood, a former member of the Army Security Agency — which deciphers signals — said he spotted four phrases or words that were repeated throughout the note, including “D.B. Cooper is not real,” “Uncle” or “Unk” referring to Uncle Sam, “the system,” and “lackey cops.”

“D.B. Cooper” and “lackey cops” appeared in the same sentence, “as did “Unk” and “the system,” suggesting to Sherwood that the coded messages could be contained in those sentences.

He decoded “through good ole Unk” to mean “by skyjacking a jet plane,” using a system of letters and numbers.

“And please tell the lackey cops” was decoded to mean “I am 1st LT Robert Rackstraw,” according to Colbert.

Sherwood had deciphered earlier letters from Cooper and had become familiar with his writing style.

“I read it two or three times and said, ‘This is Rackstraw, this is what he does,’” Sherwood told the Daily News.

“I noticed he kept on repeating words in his sentences and thought he had a code in there somewhere. He was taunting like he normally does and I thought his name was going to be in it and sure enough the numbers added up perfectly,” he said.

“I was definitely shocked his name was in there. That’s what I was looking for and everything added up to that,” he said.

An earlier letter, addressed to four different newspapers, contained hidden identifiers — including his military units — that pointed to Rackstraw, now 74 and living in the San Diego area. Rackstraw, who could not be reached for comment, was previously investigated and cleared by authorities of being Cooper, but he remains the most likely suspect in the elusive case.

“Let’s just say we closed the case and this is icing on the cake I didn’t expect, it truly is. We not only had his initials and units in the other letters, but we now have him saying, ‘I am Cooper.’ Rackstraw is a narcissistic sociopath who never thought he would be caught,” Colbert said.

“He was trying to prove that he was smarter than anyone else. But he couldn’t fight 1500 years of brainpower on our team. We beat him. I didn’t expect it, but it’s the icing.”